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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 23, 2016, 1:20 am 
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Ok, so I took my car to the track for the first time ever. I myself had never been on a race track and it was such a blast that I can't wait till next time.

So a little bit about my car. I started this project in 2008 and finish in 2014. Yeah it took a while, I had no kids when I started and now, 8 years later I got four. The car was on the back burner for quite some time. Anyway I finally finished it in October 2014 and drove about 2000km since then with no issues. I use the book size for the frame with a few mods for the IRS and I wanted a full roll bar. I used the brakes, the diff and the steering rack off of a Mazda RX7 GXL. I build my own suspension and used QA1 shocks and Hypercoils with modified RX7 spindles.
For motor, I wanted something small and light and found a almost new Kawasaki ZX14 with 1300mils on it.



On the track I notice the the car was really tail happy. I have Yokohama A048 up front and Yokohama A008P with doesn't help the back as those are street tire and the front R compound. But I notice that the car would start sliding in deceleration as soon as I would give it steering input. So I think that the LSD that came from the RX7 is the problem. It's a clutch type limited slip and is pretty much always lock up.

I don't known if others have had similar issues but I was expecting the Seven to be really fast around corner and that's where I was the slowest.
As far as balance my car is rear heavy, it weighs 1176lbs with me in it and half a tank. The rear is about 700lbs and the front 500lbs. I notice that can was sliding around even more on the track when I was by myself so it's probably not a balance problem.

Anyway here is a few pictures of the track day.


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PostPosted: September 23, 2016, 2:05 am 
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Joined: June 8, 2010, 8:02 pm
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Location: White Rock, BC, Canada
Glad you had a fun first trackday. I think most of your problem is due to the mismatched tires. That would be step one to try to correct the looseness. The next thing I would check is if your rear suspension is toe out on heavy loading. If the diff is a clutch type, you can always add some LSD additive to it to make the clutch slip more.

Cheers.

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PostPosted: September 23, 2016, 9:17 am 
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We'll need a couple of pictures of you car suspension to give you much help. Congrats on a nice looking car.

Your weight balance is not far off. You need the LSD, especially as you get better.

Cars with live axles use different front suspension setups. Other issues could be binding in the rear suspension and the location of your panhard bar. Check for binding by raising the rear onto jack stands under the frame. Raise it enoug to lift the rear tires off the ground a bit. Now jack one rear wheel upwards thru it's travel and observe wether you can do that without lifting the wheel on the other side of the car. Probably take the wheels off to make this easier.

Figure out the relative spring rates front vs. rear. if nothing else get an idea just by jumping on the car frame.

All of the above is worth looking into, getting 4 of the same tires is where to start though. R compound tires are not as soft on an 1100 lb. car, they are probably usually on heavier cars. Oh, it's not just the compound the tires may have different construction that will give you drivability issues.

You should probably be running less than 20 lbs. air pressure, maybe 18. What size are your rims and tires?

Lastly, do not drive down the straight with one hand on the top of your wheel and the other on the shifter! The absolute least time required should be used to shift - otherwise hands on the wheel.

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PostPosted: September 23, 2016, 11:03 am 
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Joined: December 29, 2007, 10:41 pm
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Location: Vancouver, BC
I can't add anything more that what's been said already. But, who put on the track day? Once my current car is finished, I'd like to take it out to Mission and see what it can do.

Rod


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PostPosted: September 23, 2016, 11:15 am 
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You said "I myself had never been on a race track." There's a strong chance that there isn't anything major wrong and is simply inexperience. Depending how twisty the course is, how well the car does can be up to 80% driver and you're already blaming the car. Driving well can take years to learn so consider having an experienced driver take it out and giving you his feedback - then we can talk again :)

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PostPosted: September 23, 2016, 1:20 pm 
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Joined: April 12, 2012, 11:56 am
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Location: Pemberton, BC
Hey Gabriel,
welcome to the forum. Nice job on the car. :cheers:
I had planned to be at the track day as well; it would have been fun to have two bike engined Sevens there, at the same time. But unfortunately, I did not get my trailer finished in time, and there is no way that I would drive through the Lower Mainland in the Seven. I can barely stand it in the Minivan. So it will have to be next year.
I agree with Marcus and Kurt, get more seat time, before you spend a lot of time making changes to the car. My racing days were a long time ago, but I remember the first time that I ran my Formula Ford around Westwood. It felt like a fire breathing, tire spinning projectile coming out of the hairpin. After a while, and a few races under my belt, it felt like my Grandmothers' Chevette, that I needed to get out of and give it an extra push to get up the hill.
Maybe you could share some more info on your build. I'm intrigued how you managed to keep your airbox under the hood. Also, your low weight is amazing. Sounds like the car is just under a thousand pounds. I have a bit more rollcage, but no windshield, and I'm not even close to that; mine is just under 1,300 lbs, but then I had it weighed on a dump truck scale. Maybe I should double check that.
How did you fare with the sound level limit? I understand that the limit at Mission is 92db. I don't think that I would meet that with my open air intake box. Yours sounds great, but a GoPro isn't the most reliable judge.

Rod,
it is the UBC Sports Car Club, and they have about 3 days during the season. Anyone can join; my only affiliation with UBC, was having a few beers in the pub many, many moons ago. Membership is only $ 25/year.

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My build log:
viewtopic.php?f=35&t=14520&start=0
My build video:
https://vimeo.com/143524140 password "matovid"


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PostPosted: September 23, 2016, 1:41 pm 
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Gabriel, great to see you getting out there and driving you car like it was designed to be. But now you will have to spend the time and effort to develop the car. Lots of Locosts are never de-bugged because there never driven hard enough often enough for the bugs to be worked out. Watching the video showed nothing out of the ordinary but we cannot tell if it was you fastest lap. But from your steering inputs you were never tail happy, plus I heard no squealing from the tires. R rated tires don't squeal much but your rears should have been audible. So were would I start

1. Matching set of tires, not R rated
2. Find the correct tire pressures (mine are 18/20)
3. Good Alignment

More track days will uncover other issues, brake bias is the one that I just uncovered, it also caused a loose feeling on turn in. Keep working thru the issues and your skills will get better as well as your car. AutoX can be a good cheap way to work out some issues, brake bias can be worked out at a $30 AutoX not a $250 track day.

One passing thought "keep your hands on the steering wheel", this is not a Saturday night cruise.

Graham


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PostPosted: September 23, 2016, 11:08 pm 
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Location: White Rock, BC, Canada
cs3tcr wrote:
I can't add anything more that what's been said already. But, who put on the track day? Once my current car is finished, I'd like to take it out to Mission and see what it can do.

Rod


UBCSCC and VCMC are probably the two most common track day providers (and autoX) at Mission. I'd also suggest looking into Bremerton, The Ridge, and PIR across the border for trackdays. Bigger tracks, and more room to screw up before stuffing it into a wall.

Cheers.

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PostPosted: September 23, 2016, 11:52 pm 
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Thanks guys for the reply's.

I think the mismatch on tire is the biggest problem here to I'll have to stop buy everything second hand and just put some decent tires on there.
I let the instructor have take a few laps and he thought the same. If you look at the video below you will see how he is trying to keep it straight. I'm not as fast as him but I can definitely feel the car when it starts to slide even if I don't have much experience. :wink:



Martin, too bad you couldn't make it would of been awesome. Is your car 1300lbs with you in it? You probably should weigh it again. Mine didn't have the windshield when I weighed it, I had to make one otherwise they weren't going to pass it with just a small deflector. I have a few pictures below of how I tucked the throttle body under the hood.

What I would like to be able to do at this point is make the car feel balanced. I think you're right Graham if I can do some AutoX that would help on the wallet a bit.

I'll try keeping my hands on the steering wheel next time. :oops:


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PostPosted: September 24, 2016, 12:02 am 
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Joined: April 26, 2014, 10:19 pm
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Location: Victoria B.C.
The IRS on my blue Deman SR7 was binding simply from the bolts being over torqued by the previous owner. The car was fine on the street, but almost undriveable at autocross. I loosened them off a bit and replaced the T-bird IRS poly bushings with Delrin. The car drives like a dream now....well balanced and controllable at the limit.

Congrats on a what looks like an amazing little car. If you ever bring it over to Vancouver Island....shoot me a PM. :mrgreen:


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PostPosted: September 24, 2016, 12:06 am 
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Hi Foxtrot,

What track is that it look very nice, I like the wing you have on there do you have a close up picture of it?


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PostPosted: September 24, 2016, 12:16 am 
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Joined: April 26, 2014, 10:19 pm
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Location: Victoria B.C.
That's the new Vancouver Island Motorsport Circuit. It's an amazing facility! http://islandmotorsportcircuit.com/

The wing made a huge difference on high speed sections of the circuit...def worth the $100 off craigslist...haha.


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PostPosted: September 24, 2016, 12:38 am 
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Joined: April 26, 2014, 4:44 pm
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Your car look awesome love the color contrast between the wheels and car. That track looks so good, how much didn't it cost you to get on there? It's definitely nicer pavement than Mission Raceway.

Next year if I can afford to go on a track like this I'll definitely make the trip over to the island.


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PostPosted: September 24, 2016, 12:57 am 
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Joined: April 26, 2014, 10:19 pm
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Location: Victoria B.C.
Thanks man! The track is pretty spendy...but I can probably get you on there if you're really keen. I'm also thinking of trying to organize a super7 track day next year....but I probably shouldn't even mention that yet. :ack:


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PostPosted: September 24, 2016, 1:04 am 
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You can count me in if you do, it would be pretty sweet to see a bunch of super 7 together on the track.


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